As for Teams, it looks like it’s much closer to Markdown (uses the same idiosyncratic/stupid link syntax), but still significantly incompatible even if they call it that. And my guess (as a non-user) is that it’s just an input method immediately converted to HTML or similar, not retained as text. So in that way it’s not Markdown either.
I get bold and italic confused because Google Chat is almost-Markdown except for * being bold and _ being italic (whereas it's double vs singular in classic Markdown).
My company is on Teams and I regularly use Markdown in my messages, though I still struggle to remember that I have to use underscores not asterisks for italics.